1. Field of the Invention
The present invention relates generally to methods for stimulating T cells to restore normal immune repertoire. The present disclosure includes methods to eliminate undesired (e.g., autoreactive, alloreactive, pathogenic) subpopulations of T cells from a mixed population of T cells, thereby restoring the normal immune repertoire of said T cells. The present invention also relates to compositions of cells, including stimulated T cells having restored immune repertoire and uses thereof.
2. Description of the Related Art
The ability of T cells to recognize the universe of antigens associated with various cancers or infectious organisms is conferred by its T cell antigen receptor (TCR), which is made up of both an α (alpha) chain and a β (beta) chain or a γ (gamma) and a δ (delta) chain. The proteins which make up these chains are encoded by DNA, which employs a unique mechanism for generating the tremendous diversity of the TCR. This multisubunit immune recognition receptor associates with the CD3 complex and binds to peptides presented by the major histocompatibility complex (MHC) class I and II proteins on the surface of antigen-presenting cells (APCs). Binding of TCR to the antigenic peptide on the APC is the central event in T cell activation, which occurs at an immunological synapse at the point of contact between the T cell and the APC.
To sustain T cell activation, T lymphocytes typically require a second co-stimulatory signal. Co-stimulation is typically necessary for a T helper cell to produce sufficient cytokine levels that induce clonal expansion. Bretscher, Immunol. Today 13:74, 1992; June et al., Immunol. Today 15:321, 1994. The major co-stimulatory signal occurs when a member of the B7 family ligands (CD80 (B7.1) or CD86 (B7.2)) on an activated antigen-presenting cell (APC) binds to CD28 on a T cell.
Methods of stimulating the expansion of certain subsets of T cells have the potential to generate a variety of T cell compositions useful in immunotherapy. Successful immunotherapy can be aided by increasing the reactivity and quantity of T cells by efficient stimulation. Furthermore, in the settings of autoimmunity or transplantation, successful immunotherapy can be aided by the elimination of unwanted autoreactive or alloreactive cells.
The various techniques available for expanding human T cells have relied primarily on the use of accessory cells and/or exogenous growth factors, such as interleukin-2 (IL-2). IL-2 has been used together with an anti-CD3 antibody to stimulate T cell proliferation, predominantly expanding the CD8+ subpopulation of T cells. Both the APC signals directed towards the TCR/CD3 complex and CD28 on the surface of T cells are thought to be required for optimal T cell activation, expansion, and long-term survival of the T cells upon re-infusion. The requirement for MHC-matched APCs as accessory cells presents a significant problem for long-term culture systems because APCs are relatively short-lived. Therefore, in a long-term culture system, APCs must be continually obtained from a source and replenished. The necessity for a renewable supply of accessory cells is problematic for treatment of immunodeficiencies in which accessory cells are affected. In addition, when treating viral infection, if accessory cells carry the virus, the cells may contaminate the entire T cell population during long-term culture.
In the absence of exogenous growth factors or accessory cells, a co-stimulatory signal may be delivered to a T cell population, for example, by exposing the cells to a CD3 ligand and a CD28 ligand attached to a solid phase surface, such as a bead. See C. June, et al. (U.S. Pat. No. 5,858,358); C. June et al. WO 99/953823. While these methods are capable of achieving therapeutically useful T cell populations, increased robustness and ease of T cell preparation remain less than ideal.
Methods previously available in the art have made use of anti-CD3 and anti CD28 for the expansion of T cells. In addition, the methods currently available in the art have not focused on short-term expansion of T cells or obtaining a more robust population of T cells and the beneficial results thereof. None of these methods has described using such or similar methods to eliminate an undesired clonal or oligoclonal T cell population from a T cell population nor the beneficial results thereof. Moreover, the methods previously available tend to further skew the clonality of the T cell population rather than eliminate undesired reactive clones from a T cell population, and restore a normal immune repertoire. For maximum in vivo effectiveness, theoretically, an ex vivo- or in vivo-generated, activated T cell population should be in a state that can maximally orchestrate an immune response to cancer, infectious disease, or other disease states. In the setting of autoimmunity or transplantation, the activated T cell populations should be in a state to reconstitute a normal T cell repertoire with a reduced presence or entirely without the presence of autoreactive or potentially pathogenic alloreactive T cells. Currently, patients with autoimmune diseases are treated with long-term immunosuppression to inhibit the autoreactive T cells that cause disease. When the immunosuppressive agents are stopped, disease recurs often concomitant with reappearance of disease causing T cells that re-emerge in these patients. The major problem in hematopoietic stem cell transplantation is graft-versus-host disease (GVHD), which is caused by alloreactive T cells present in the infused hematopoietic stem cell preparation. In organ transplantation, graft rejection mediated by alloreactive host T cells is the major problem, usually overcome by long-term immunosuppression of the transplant recipient.
The present invention provides methods to generate an increased number of more highly activated and more pure T cells that have surface receptor and cytokine production characteristics that appear more healthy and natural than other expansion methods and further provides for the diminution or elimination of undesired autoreactive or alloreactive populations of T cells. The present invention provides methods for the use of said populations of T cells in the setting of autoimmune diseases, hematopoietic stem cell, and organ transplantation, as well as other settings where reconstitution of an ablated, abrogated, or otherwise dysfunctional T cell immune system is desired. In addition, the present invention provides compositions of cell populations of any target cell, including T cell populations and parameters for producing the same, as well as providing other related advantages.
Additionally, it is becoming well recognized that the aging immune system is characterized by a progressive decline in the responsiveness to exogenous antigens and tumors in combination with a paradoxical increase in autoimmunity (C. Weyand et al. Mechanisms of Ageing and Development 102:131-147, 1998; D. Schmidt et al. Molecular Medicine 2:608-618, 1996; G. Liuzzo et al. Circulation 100:2135-2139, 1999). These studies have described that aging is associated with the emergence of a subset of T helper cells that are characterized by the loss of CD28 expression. CD4+CD28− T cells are long lived, typically undergo clonal expansion in vivo, and react to auto-antigens in vitro. The loss of CD28 expression is correlated with a lack of CD40 ligand expression rendering these CD4+ T cells incapable of promoting B cell differentiation and immunoglobulin secretion. Aging-related accumulation of CD4+ CD28− T cells results in an immune compartment that is skewed towards auto-reactive responses and away from the generation of high-affinity B cell responses against exogenous antigens.